Linear drive

ABSTRACT

A linear drive, which has a housing ( 2 ) delimiting a receptacle ( 4 ), in which the drive means ( 6 ) are arranged and from which the force or power transmitting member ( 12 ) extends, which cooperates with the drive means ( 6 ). The drive means ( 6 ) are a component of an electrical linear motor ( 18 ) which as a cartridge-like unit ( 22 ) is inserted is into the receptacle and secured in place in relation to the housing.

FIELD OF THE INVENTION

The invention relates to a linear drive comprising a housing, whichdefines a receptacle, in which drive means are arranged and out of whichat least one axial end region of a power transmission member, which isadapted to cooperate with the drive means, extends.

BACKGROUND OF THE INVENTION

Linear drives of this type are in wide use in the form of fluid powercomponents, that is to say components operated by fluid. One possibledesign is to be found in the German patent publication (utility model)29,706,098.8, which involves a linear drive designed in the form of aslide drive device and whose principal housing body comprises acylindrical receptacle, wherein a piston constituting the drive meansslides. A rod-like power or force transmitting member, connected withthe piston, extends at its end out of the principal housing body and isable to be coupled with an object to be moved.

The actuation of the linear drive is performed by the action of a fluidon the piston and for positioning external abutments are provided.

In the case of linear drives of this type there is usually the problemthat more especially in the case of pneumatic operation precisepositioning of the power transmitting member is difficult and that slowmovement of the piston tends to be jerky, this impairing exact motionand positioning.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a linear drive of thetype initially mentioned, which facilitates any necessary positioningmeasures and more especially renders possible jerk-free motion even atlow speeds. This is to be combined with a simple structure of thearrangement, which is simple to assemble and fit.

In order to attain this object there is the provision in accordance withthe characterizing part of claim 1 that the drive means are componentsof a linear electric motor, which is mounted in the receptacle as acartridge-like unit and is fixed in relation to the housing.

Departing from the said prior art there is therefore an electricallinear drive, whose drive means belong to a so-called linear motor—aparticular design of an electric motor—in the case of which the armaturedoes not perform a rotary but rather a linear movement. The drive forceis provided by a travelling magnetic field, this meaning that even inthe case of slow motion there is a freedom from jerks and there ispossibility of extremely smooth movement. Furthermore, such a linearmotor is also characterized by low wear and reduced need for servicing.

It is furthermore an advantage in the invention that the linear motordoes not have its individual parts fixed to the housing and is in factinserted into it like a cartridge, the housing not having to perform anyimportant operational function for the electrical drive principle of thelinear motor. Accordingly it is possible for the housing to possess aconfiguration in accordance with the intended purpose of use, theexternal form not having to be different to that of a comparable fluidpower linear drive and it is only instead of the drive means in the caseof fluid power linear drive means the electrical linear motor may beemployed. In this respect it is an advantage that in case of need, onthe basis of a uniform housing, a fluid power or an electrical lineardrive may be produced, that is to say with the possibility of employinga large number of identical parts. Finally, it is to be noted as anadvantage that lost time due to a defect in the drive means andinvolving failure to operate of the linear drive may be veryconsiderably reduced, because the cartridge-like linear motor unit maybe simply and rapidly replaced.

Although the German patent publication 19,512,080 A1 discloses anelectrical linear drive, in whose housing an electrical drive isinserted, recourse is had here to a conventional electric motor with arotating drive shaft and furthermore there is no design in the form of acartridge-like unit.

Further advantageous developments of the invention are defined in thedependent claims.

The linear motor preferably possesses a tubular or sleeve-like motorhousing extending along at least part of its length, which extends intothe receptacle in the housing, optimum fitting in place being ensuredbecause the shape thereof is complementary to the internal shape of thereceptacle space. In this respect it is preferred to employ a circularcross sectional shape owing to the possibility then offered ofparticularly simple manufacture. It would be feasible also however tohave cross sectional forms departing from a circular one, moreparticularly if using simple means it is desired for the linear motorunit to be locked in rotation in relation to the housing.

Insertion of the linear motor into the receptacle may take place as partof a strictly linear plugging operation and/or for example by screwingin so that the assembly movement is combined with a rotary one. In thiscase it is possible for a suitable screw thread to be provided on theouter periphery of the motor housing to cooperate with a mating threadon the housing.

It is convenient for the receptacle, which preferably extends along atleast the major part of the length of the linear motor, to be closedperipherally along its entire length, i. e. not interrupted by slot. Itis possible to avoid having a special purpose design and there is thepossibility of having recourse to the comparable body of a conventionalfluid power linear drive for the housing.

The receptacle is preferably constituted by an elongated receptaclespace extending in a principal housing body of the housing, into whichspace the linear motor unit is inserted like a cartridge coaxially fromone end. In the case of the principal housing body it is preferably aquestion of extruded section, into which the receptacle space isproduced in an axially continuous form.

It is preferred for the linear member to possess a motor housingarranged at least for the greater part of the length thereof in theinterior of receptacle space, the power transmitting member extendingfrom one end of it while adjacent to other end there are electricalterminal means for the supply and/or output of electrical signals, theelectrical terminal means preferably being part of a compact couplingmeans.

Operation with a high degree of accuracy is possible, if the powertransmitting member engages a guide slide, which slides externally onthe housing linearly. Such a guide slide or carriage can also take uptransverse forces so that the drive means, cooperating with the powertransmitting member, of the linear motor can be kept substantially freeof transverse loads causing wear.

Frequently electrical linear drives are in competition with fluid powerlinear motors, the use of one or the other type being specified bymarginal conditions of the respective application. One seriousdisadvantage in connection with this is that the different types, asconfirmed by the German patent publication (utility model) 29,706,098.8and the German patent publication 19,512,080 A1, are extremely differentso that the manufacturer do not supply both types in all overall sizesand the user is obliged to make extensive design changes in drivesystems for adopting a different sort of drive. The electrical lineardrive in accordance with the invention does offer the advantage herethat for the production thereof recourse may be had to a singleprincipal housing body, which may be employed alternatively as well asthe principal housing body of a fluid power linear drive. For thispurpose there is a provision such that the principal housing bodies inboth types of linear drive are the same in their outer shape at leastand the receptacle spaces provided in the principal housing bodies ofthe linear drive possess the same cross sectional form. Accordingly forthe manufacture of the principal housing bodies one may resort tosubstantially identical steps and tools, this meaning that there is alsocompatibility for the user. The identical cross sectional form of thereceptacle spaces leads to a flexible manufacture, since, dependent onthe type of design, it is merely necessary for fluid power orelectrically operated drive means to be inserted.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described with reference to theaccompanying drawings in detail.

FIG. 1 shows a preferred design of an electrical limit drive in anoblique perspective rear view, the electrical linear motor employedbeing illustrated in an intermediate position assumed in the course ofassembly.

FIG. 2 shows the linear drive of FIG. 1 in a longitudinal section takenin a horizontal plane as indicated by the section line II—II.

FIG. 3 shows the linear drive of FIGS. 1 and 2 in cross section on thesection line III—III of FIG. 2.

FIG. 4 shows a fluid power linear drive in a longitudinal sectional viewsimilar to that of FIGS. 1 through 3, which while having a differentdrive means, is otherwise identical.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The electrical linear drive depicted in FIGS. 1 through 43 and the fluidpower linear drive 1′ illustrated in FIG. 4 respectively possess ahousing generally referenced 2, having a principle housing body 3preferably in the form of an extruded section. The same preferablyconsists of an aluminum alloy.

The housing 2 delimits an elongated receptacle 4, which is convenientlyconstituted by an elongated receptacle space 5 axially extending throughthe principal housing body 3 and which may be formed in the course ofproduction of the principal housing body by extrusion. The receptaclespace 5 is preferably peripherally complete or closed for the whole ofits length.

In the interior of the receptacle 4 drive means 6 and 6′ are arranged,which are able to be driven by the supply of external energy to performa reciprocating linear movement 7 as indicated by the double arrow alongthe longitudinal axis 8 of the receptacle 4 or, respectively, of thereceptacle space 5. The linear movement 7 may be transmitted to apreferably rod-like transmission member 12 by connection outside thehousing 2, such member 12 being permanently connected with the drivemember 6 and 6′ axially and extending out at that axial end part 14 ofthe receptacle 4, which is associated with the end of the principalhousing body 3, which in the following is referred to as the front side13.

On the outer end of the power or force transmitting member 12 it wouldbe possible to attach a component to be moved. In order to enhance theaccuracy of motion and to reduce wear of the drive means 6 and 6′ and ofthe power transmitting member 12 it is however an advantage if thesection, which is to the outside of the receptacle 4, of the powertransmitting member 12 is, in manner comparable with the workingembodiments, secured to a guide slide 15 (at the attachment point 16),which for its part slides on the principal housing body 3 in a directionparallel to the longitudinal axis 8 with the aid of an intermediatelinear guide 17.

It is convenient for the guide slide 15 to overlap the principle housingbody 3 in the axial direction, the degree of overlap being dependent onthe instantaneous position in the stroke of the associated drive means 6and 6′. The guide slide 15 is suitable for the attachment of anycomponents to be moved, the linear guide means 17 taking up anytransverse forces so that the drive side is kept free of loads in thisrespect.

In the In the working examples the arrangement is such that the drivepart comprising the drive means 6 and 6′ and the guide part, comprisingthe longitudinal guide means 17 means of the respective linear drive 1and 1′, are arranged alongside each other so that there is aparticularly low or flat design. Other arrangements would however bepossible as well, as for instance a guide slide extending above thedrive part.

The electrical linear drive 1 of FIGS. 1 through 3 is more particularlycharacterized by its drive means 6 being a component of an electricallinear motor 18, which as a cartridge-like unit—referred to in whatfollows as a linear motor unit 22—is inserted into the receptacle 4 andis fixed in the housing. All drive parts are accordingly collectedtogether compactly and in the illustrated working example are insertedfrom one of the two terminal openings 23 and 24 coaxially into thereceptacle space 5.

It is in this manner that the fitting and assembly of the electricallinear drive 1 is extremely simple and interruptions in operation due toservicing are substantially reduced, because in the case of there beinga defect rapid replacement of the linear motor unit 22 may take place.In the case of the illustrated working embodiment the linear motor unit22 is inserted via the opening 23 at the rear side 25 of the principalhousing body 2 into the receptacle space 5. In this respect the overalllength of the linear motor 18 is so matched to the overall length of theprincipal housing body 3 that it is for a major part taken up in theinterior of the receptacle space 5.

In the illustrated working embodiment the arrangement is such that themotor housing 26 of the linear motor is completely taken up within thereceptacle space 5 and only an interface body 27, which adjoins the rearof the motor housing 26, extends past the principal housing body 3. Theinterface body 27 possesses electrical terminal means 28, indicated onlydiagrammatically, which serve for the supply and/or output of signalsemployed for the operation of the linear motor 18. Electrical actuatingsignals are regularly supplied via the electrical terminal means, whichbring about a linear stroke movement of the drive means 6. Furthermoreit is possible for detection signals to be supplied, which stem from aposition detecting means integrated in the linear motor 18, and with theaid of which an exact positioning of the drive means 6, and of the forcetransmitting member 12 connected with it, is possible.

The electrical terminal means 28 may, as illustrated, be a component ofa multi-pole or multi-pin coupling means, which is more especiallydesigned in the form of a plug element.

The mounting of the linear motor 18 fixed to the housing may beperformed using any desired attachment means. In the illustrated workingembodiment it is ensured by screwing the linear motor 18 together withits motor housing 26 in the receptacle space 26. For this purpose on itsouter periphery the motor housing 26 possesses an external screw thread32, which is preferably limited to the rear end part of the motorhousing 26 and which fits into a complementary internal screw thread 33provided in the rear axial end part 34 of the receptacle space 5.Accordingly assembly is performed by a combined plugging and screwingoperation, the linear motor 18 being moved with its thread-free frontpart to the fore and plugged through rear opening 23 in the receptacle 4until the external thread 32 makes contact with the internal thread 33following which the motor housing 26 is also turned about thelongitudinal axis until the two threads are screwed together and boththe axial and also the angular position of the motor housing 26 are setin relation to the principal housing body 3. The axial position may herebe predetermined by the set length of the thread or by separate abutmentmeans not illustrated in detail.

More especially in the case of an embodiment, in which linear motor 18is placed in the receptacle 4 using at least a rotary movement, it is anadvantage if at least the length section within receptacle the 4, of themotor housing 26 possesses a circular outer form. This circularlycylindrical length section then means that the motor housing 26 may makevery adequate contact with the inner face of the receptacle space 5, if,as illustrated, the internal shape of the space 5 is made complementaryto the outer shape of the respective length section of the motor housing26.

However, designs are also possible, in the case of which the inner crosssectional shape of the receptacle space 5 and the outer cross sectionalshape of the length section, associated with it, of the motor housing 26are non-circular, oval or polygonal forms and more especiallyrectangular or square configurations being possible. Such designsfurthermore possess the advantage that the angular position of the motorhousing 26 is automatically predetermined on assembly and simultaneouslythe angular position is locked.

Owing to the exact adaptation of the cross sectional shapes it ispossible to ensure that the linear motor 18 is well held in thetransverse direction and is secured in position even when the attachmentmeans (threads 32 and 33), serving for axial fixation, are restricted tothe end part of the motor housing 26.

The linear motor may be of any known) type, as for example a designindicated in the schedule of types designated as “LinearantriebeLinMot-P” of the Sulzer “Electronics AG Company”. Preferably the linearmotor operates in accordance with the electrodynamic principle, thereaction forces being directed to a permanent magnet arrangement 35. Thedrive means 6 are constituted for instance by a piston-like armature 36,which bears the said permanent magnet arrangement 35, which is bestcomposed of a plurality of coaxially following and preferably segmentedannular permanent magnets 37, which are radially magnetized, thedirection of magnetization of sequentially following permanent magnet 37being opposite.

The permanent magnet arrangement 35 is mounted on a carrier, which inthe working example is constituted by a section of the length of theforce transmitting 12.

The armature 36 is located in the interior of a tubular section 38 ofthe length of the motor housing 26, which is preferably made of steelmaterial and forms an magnetic return circuit. On the inner face of thetubular section 38 there is a tubular coil arrangement 42 surroundingthe armature 36 coaxially with a radial play and consisting of aplurality of sequential coil parts 43, whose axial width is best madeequal to half the width of the individual permanent magnets 37. The coilparts are in the working example placed in series in halves, one half ofthe coils again having a reversed direction of the magnetization toproduce a uniform direction of action of the force. Operation is bymeans of electrical voltage signals, which are supplied via theelectrical terminal means 28 and produce the effect that a travelingfield causes the linear drive of the armature 36 in the one or in theother axial direction in relation to the coil arrangement 42 and to themotor housing 26.

In a complementary manner the coil arrangement 42 can be so designedthat it works via detection of the position of the armature 36 so thatit is possible to speak of a position detection means integrated in thedrive motor.

It will be clear that the electrical linear drive renders possible adesign which is identical to that of fluid power drives and for instancepneumatic linear drives so that on the basis of identical basic parts itis possible for linear drives with an electrical or a fluid power mannerof operation to be manufactured in a rational and flexible manner. Thisis made particularly clear in FIG. 4, which illustrates a fluid powerlinear drive 1′, whose design is the same as that of the electricaldrive illustrated in FIGS. 1 through 3 with the exception of thedifferent drive means.

In the case of the linear drive 1′ of FIG. 4 the componentscorresponding to those of the electrical linear drive 1 are referencedidentically. As will be readily apparent, the combination of the guideslide 15 and the principal housing body 3 is identical in both types oflinear drive 1 and 1′. Instead of the electrically operated drive means6 however fluid operated drive means 6′ are employed, which in theworking example are constituted by a piston 44, which runs in thereceptacle 4 and makes sliding contact with the inner peripheral face ofthe receptacle space 5. The linear motor unit 22 is in this casecompletely removed and the force transmitting member 12 comprises apiston rod, which at one end is attached to the piston 44 and at theother end engages the guide slide 15.

Compared with the electrical linear drive 1 the outer configuration ofthe fluid power linear drive 1′ is at least essentially and preferablycompletely identical and as a further point of agreement both thereceptacle spaces 5 possess the same cross sectional form. There isaccordingly the possibility—on the basis of one and the same overallsize of housing 2—of selectively using an electric linear motor 18 or apiston 44 in the receptacle space 5 and accordingly of selecting themanner of operation of the linear drive as may be required.

In the interior of the principal housing body 3 fluid ducts 45 and 46are formed, which are only employed in the case of application as afluid power linear drive 1′ and in the case of use as an electricallinear drive 1 remain unused. In the case of use as a fluid power lineardrive 1 in accordance with FIG. 4 they serve for the supply and/oroutput of the fluid and more particularly pneumatic pressure mediumsupplying the drive force for the piston 44.

Each of the two fluid ducts 45 and 46 extends in the interior of theprincipal housing body 3 between an external face—here the rear side25—of the housing and one of two working spaces 47 and 48, which thepiston 44 separates from each other in the receptacle space 5. At itstwo axial end parts 14 and 34 the receptacle space 5 is respectivelyclosed by a terminal wall 49 and 59, fixed in relation to the housing,each of such terminal walls 49 and 50 constituting a limiting wall,opposite to the piston 4, for one of the working spaces 47 and 48.Accordingly it is possible—via the external duct openings, with whichfluid ducts leading to other equipment may be connected—for the supplyof fluid to the working spaces 47 and 48 and accordingly of the axialstroke motion of the piston 44 and of the force transmitting member 12,to be controlled.

The rear terminal wall 50 is designed like a cover and is moreespecially inserted axially into the receptacle space 5 so that itpreferably does not extend past the rear side 25. Attachment isperformed using a screw connection, the above mentioned internal screw33 thread being employed, into which the rear terminal wall 50 isscrewed using a complementary external screw thread 54.

Using a similar screw attachment the front terminal wall 49 is alsofixed to the principal housing body 3, since its external screw 52 isscrewed into the front end part 14, provided with a internal screwthread 53, of the receptacle space 5. This internal screw thread 53 maybe left unused in the case of a linear drive of the electrical type inaccordance with FIGS. 1 through 3.

The front terminal wall 49 of the housing 2 is designed in the form ofan annular member or a sleeve, it surrounding the rod-like forcetransmitting member 12 with a sealing effect. Furthermore the frontterminal wall 49 preferably has its full length within the receptaclespace 5 axially.

It is clear that there is therefore a possibility of producing aplurality of linear drives able to be employed independently from eachother, and including at least one electrical linear drive 1 and at leastone fluid power linear drive 1′, such two linear drives beingessentially identical as regards their outer configuration so that inmanufacture it is possible to use, at least to a predominant extent,identical parts and accordingly identical tooling and moreover at thesite of application there will be compatibility of installationmeasures. The identical cross section of the receptacles in the twocases here offers the possibility of installing, selectively,electrically actuated drive means 6 or fluid power drive means 6′,something which lead to a high degree of flexibility in the case of theproduction of linear drives. If the electrical drive means includeelectrical linear motors compactly assembled as a cartridge, assemblyand fitting is particularly simplified, because assembly by insertion ispossible and this saves time.

What is claimed is:
 1. A linear drive comprising a housing (2), whichdefines a receptacle (4), in which drive means (6) are arranged and outof which at least one axial end part (14) of a power transmitting member(12), which is adapted to cooperate with the drive means (6), extends,wherein the drive means (6) are components of a linear electric motor(18), which is mounted in the receptacle (4) as a cartridge-like unit(22) and is fixed in relation to the housing and wherein the motorincluding a motor housing (26), being received in the receptacle (4) andhaving an outer shape complementary to the inner shape of the receptacle(4).
 2. The linear drive as claimed in claim 1, characterized in thatthe cross sectional form of the receptacle (4) and of the length sectiontherein of the motor housing (26) is circular.
 3. The linear drive asclaimed in claim 1, characterized in that the cross sectional form ofthe receptacle (4) and of the length section arranged therein of themotor housing (26) is not circular and in this respect preferably ovalor rectangular in design.
 4. The linear drive as claimed in claim 1,characterized in that the linear motor (18) is plugged and/or screwedinto the receptacle (4).
 5. The linear drive as claimed in claim 1,characterized in that the receptacle (4) has an unbroken periphery forits entire length.
 6. The linear drive as claimed in claim 1,characterized in that the receptacle (4) is constituted by an elongatedreceptacle space (5) extending in a principal housing body (3) of thehousing (2), into which space the cartridge-like linear motor unit (22)is inserted coaxially.
 7. The linear drive as claimed in claim 6,characterized in that the linear motor (18) has a motor housing (26)arranged at least for a major part of its length in the interior of thereceptacle space (5) and from one end of the housing the forcetransmitting member (12) extends out and at the other end has electricalterminal means (28) for the supply and/or output of electrical signals.8. The linear drive as claimed in claim 7, characterized in that theelectrical terminal means (28) are components of a coupling means, whichis more particularly in the form of a plug means.
 9. The linear drive asclaimed in claim 6, characterized in that the receptacle space (5)extends through the principal housing body (3) in the longitudinaldirection completely.
 10. The linear drive as claimed in claim 6,characterized in that the principal housing body (3) is an extruded bodyconsisting more especially of aluminum.
 11. The linear drive as claimedin claim 6, characterized in that the electrical linear motor (18) doesnot extend out of the receptacle space (5) or only does so to a slightextent.
 12. The linear drive as claimed in claim 1, characterized inthat the drive means (6) of the electrical linear motor comprise a coilarrangement (42) mounted in a stationary manner on the motor housing(26) and a linearly moving armature (36) cooperating with the forcetransmitting member (12) and having a permanent magnet arrangement (35).13. The linear drive as claimed in claim 1, characterized in that theforce transmitting member (12) engages a guide slide (15) which isarranged externally on the housing (2) for linear sliding motion. 14.The linear drive as claims in claim 1, characterized in that it is acomponent of a plurality of mutually separately usable linear drive (1and 1′) including, in addition to the electrical linear drive (1)furthermore at least one fluid power linear drive (1′), whose principalhousing body (3) has receptacle space (5) for fluid operated drive means(6′), the principal housing body (3) of the electrical linear drive andof the fluid power linear drive (1 and 1′) being at least substantiallyidentical as regards their external form and the receptacle spaces (5)of the two linear drives (1 and 1′) possess the same cross sectionalform.
 15. The linear drive as claims in claim 14, characterized in thatthe combination of guide slide (15) and principal housing body (3) isidentical in the case of the electrical and of the fluid power lineardrive (1 and 1′).
 16. The linear drive as claimed in claim 14,characterized in that the drive means (6′) of the fluid power lineardrive (1′) comprise an axially sliding piston (44) running on the innerperiphery of the receptacle space (5).
 17. The linear drive as claimedin claim 14, characterized in that the receptacle space (5) of the fluidpower linear drive (1′) is sealed off at both axial end parts (14 and34) by means of terminal walls (49 and 50) fixed to the principalhousing body, such walls preferably extending axially into thereceptacle space (5).
 18. A linear drive comprising: a housing defininga receptacle drive means securably mountable in the housing having apower transmitting member extending out of at least one drive meansaxial end part, and the drive means including a linear electric motor,which is mounted in the receptacle as a cartridge-like unit, and whereinthe drive means has an accessible portion extending from the housingwhen secured thereto to facilitate securing and removal of the drivemeans with respect to the housing.